JP2019207359A - Mask blank, phase shift mask, and method for manufacturing semiconductor device - Google Patents

Abstract

To provide a mask blank having a phase shift film that has a function of transmitting exposure light from an ArF excimer laser at a predetermined transmittance as well as a function of generating a predetermined phase difference in the transmitted exposure light from the ArF excimer laser and that has a reduced back surface reflectance.SOLUTION: The phase shift film includes a stacked structure of a first layer, a second layer and a third layer, successively from a light-transmitting substrate side. Refractive indices n, nand nof the first layer, the second layer and the third layer, respectively, at a wavelength of the exposure light from an ArF excimer laser satisfy relationships of n>nand n<n; extinction coefficients k, kand kof the first layer, the second layer and the third layer, respectively, at a wavelength of the exposure light satisfy relationships of k<kand k>k; and film thicknesses d, dand dof the first layer, second layer and third layer, respectively, satisfy relationships of d<dand d<d.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a mask blank and a phase shift mask manufactured using the mask blank. The present invention also relates to a method of manufacturing a semiconductor device using the phase shift mask.

  Generally, in a semiconductor device manufacturing process, a fine pattern is formed using a photolithography method. Further, a number of substrates called transfer masks are usually used for forming this fine pattern. In order to miniaturize the pattern of a semiconductor device, it is necessary to shorten the wavelength of an exposure light source used in photolithography in addition to miniaturization of a mask pattern formed on a transfer mask. In recent years, as an exposure light source for manufacturing semiconductor devices, the wavelength has been shortened from an KrF excimer laser (wavelength 248 nm) to an ArF excimer laser (wavelength 193 nm).

As a type of transfer mask, a halftone phase shift mask is known in addition to a binary mask having a light-shielding pattern made of a chromium-based material on a conventional translucent substrate.
Patent Document 1 discloses a binary mask blank including a light shielding film and front and back antireflection films. In this Patent Document 1, in order to suppress flare that affects adjacent shots caused by reflection from the light shielding band and over exposure error (Dose Error) within the pattern area, It is formed in contact with silicon, transition metal, oxygen and nitrogen, the refractive index n ₂ of the film is 1.0 to 3.5, the extinction coefficient k ₂ of the film is 2.5 or less, and the film thickness t ₂ is 5 to 5. A back surface antireflection film having a thickness of 40 nm is provided. The reflectance (hereinafter referred to as back surface reflectance) with respect to the incidence of light from the transparent substrate side is about 30% or less. Specifically, as shown in the embodiment, the reflectance is about 29% or about 23. % Binary mask blank is realized.

  In Patent Document 2, a phase shift film having a function of transmitting ArF exposure light at a predetermined transmittance and causing a predetermined amount of phase shift to the transmitted ArF exposure light is provided on a translucent substrate. A disclosed halftone phase shift mask blank is disclosed. In Patent Document 2, the phase shift film has a laminated structure including a high transmission layer and a low transmission layer. Further, a SiN film having a relatively high nitrogen content is applied to the high transmission layer, and a SiN film having a relatively low nitrogen content is applied to the low transmission layer.

  In recent years, illumination systems used when performing exposure transfer on a resist film on a semiconductor device have become more sophisticated and complex. Patent Document 3 discloses a method of configuring an irradiation source of a lithographic apparatus in order to improve image formation of a mask pattern on a substrate. The method divides the illumination source into pixel groups, each pixel group including one or more illumination source points on the pupil plane of the illumination source, and changing the polarization state of each pixel group. Determining a gradual effect for each of the plurality of critical dimensions resulting from a change in polarization state of each pixel group, and using the determined gradual effect, a first plurality for each of the plurality of critical dimensions Calculating the sensitivity factor of the first illumination source, selecting the initial illumination source, and using the calculated first plurality of sensitivity coefficients, as a result of the change in polarization state of the pixel group of the initial illumination source. Repeatedly calculating a metric, wherein a change in polarization state of a pixel group of the initial illumination source generates a modified illumination source, and a repeater Based on the results in which a step of adjusting the initial radiation source.

Japanese Patent No. 5054766 JP 2014-137388 A JP 2012-74695 A

  In recent years, further miniaturization of transfer patterns has been desired, and illumination systems used for exposure transfer have become more sophisticated and complicated. For example, in the illumination system in Patent Document 3, control is performed so as to optimize the position and angle of the irradiation source. In such a complicated illumination system, when exposure is performed on the transfer mask with exposure light of an ArF excimer laser having a relatively short wavelength, stray light due to multiple reflection occurs in the translucent substrate of the transfer mask. It has become easier. When exposure transfer is performed on a resist film on a semiconductor device, if this stray light reaches a bar code or alignment mark provided outside the pattern formation region on the translucent substrate of the transfer mask, the resist film on the semiconductor device The phenomenon of reflection occurs. When this phenomenon occurs, CD variation occurs in the resist film on the semiconductor device. Since barcodes and alignment marks formed on a thin film on a light-transmitting substrate are indispensable for identification and alignment of a transfer mask, it is not realistic to remove them. In general, an illumination system used when performing exposure transfer is provided with a shutter mechanism for blocking exposure light from being exposed to the outside of the exposure area of the transfer mask. However, due to the increase in the oblique incident component of the exposure light by optimizing the position and angle of the irradiation source described above, the exposure light irradiated in the exposure area of the transfer mask is an area outside the exposure area in the translucent substrate. It is difficult to suppress stray light caused by multiple reflection. Under such circumstances, it has become difficult to satisfy the demand for further miniaturization of the transfer pattern with a mask blank having a back surface reflectance of about 30%, which has been conventionally allowed.

  Therefore, the present invention has been made to solve the conventional problems, and in a mask blank having a phase shift film on a translucent substrate, the exposure light of ArF excimer laser has a predetermined transmittance. Provided is a phase shift film having a function of transmitting and a function of generating a predetermined phase difference with respect to the exposure light of the transmitted ArF excimer laser, and further provides a mask blank including a phase shift film having a reduced back surface reflectance. The purpose is that. Moreover, it aims at providing the phase shift mask manufactured using this mask blank. An object of the present invention is to provide a method of manufacturing a semiconductor device using such a phase shift mask.

In order to achieve the above object, the present invention has the following configuration.
(Configuration 1)
A mask blank provided with a phase shift film on a translucent substrate,
The phase shift film includes a structure in which a first layer, a second layer, and a third layer are stacked in this order from the translucent substrate side,
When the refractive indexes at the wavelengths of the exposure light of the ArF excimer laser of the first layer, the second layer, and the third layer are n ₁ , n ₂ , and n ₃ , respectively, n ₁ > n ₂ and n ₂ <n _Satisfying the relationship of ₃
When extinction coefficients at the wavelengths of the exposure light of the first layer, the second layer, and the third layer are k ₁ , k ₂ , and k ₃ , respectively, k ₁ <k ₂ and k ₂ > k ₃ Meet relationships,
When the film thicknesses of the first layer, the second layer, and the third layer are d ₁ , d ₂ , and d ₃ , respectively, the relationship of d ₁ <d ₃ and d ₂ <d ₃ is satisfied. Mask blank to be used.

(Configuration 2)
It said third layer thickness d ₃ of the arrangement 1, wherein the mask blank wherein the at first layer 2 times or more the thickness d ₁ of the.
(Configuration 3)
The thickness d ₂ of the second layer, the mask blank according to Structure 1 or 2, characterized in that at 20nm or less.

(Configuration 4)
Refractive index _{n 1} of the first layer is 2.0 or more, the extinction coefficient _{k 1} of the first layer is 0.5 or less, the refractive index _{n 2} of the second layer is less than 2.0 The extinction coefficient k ₂ of the second layer is 1.0 or more, the refractive index n ₃ of the third layer is 2.0 or more, and the extinction coefficient k ₃ of the third layer is 0. 5. The mask blank according to any one of configurations 1 to 3, wherein the mask blank is 5 or less.
(Configuration 5)
The phase shift film has a function of transmitting the exposure light with a transmittance of 2% or more, and the exposure light transmitted through the phase shift film has passed through the air by the same distance as the thickness of the phase shift film. 5. The mask blank according to claim 1, wherein the mask blank has a function of causing a phase difference of 150 ° to 200 ° with respect to the exposure light.

(Configuration 6)
The mask blank according to any one of configurations 1 to 5, wherein the first layer is provided in contact with a surface of the translucent substrate.
(Configuration 7)
The first layer, the second layer, and the third layer are formed of a material composed of silicon and nitrogen, or a material composed of one or more elements selected from a semi-metallic element and a nonmetallic element, and silicon and nitrogen. The mask blank according to Configuration 7, wherein the mask blank is provided.

(Configuration 8)
The mask blank according to any one of configurations 1 to 7, wherein the nitrogen content of the second layer is less than the nitrogen content of any of the first layer and the third layer.
(Configuration 9)
The phase shift film includes a fourth layer on the third layer,
When the refractive index in the wavelength of the exposure light of the fourth layer was _{n 4,} satisfies the n 1> _{n 4} and _n 3> _{n 4} relationship,
9. The structure according to claim 1, wherein the relationship of k ₁ > k ₄ and k ₃ > k ₄ is satisfied, where k ₄ is an extinction coefficient at the wavelength of the exposure light of the fourth layer. Mask blank.

(Configuration 10)
The refractive index of the fourth layer n ₄ is 1.8 or less, the mask blank of Structure 9, wherein the extinction coefficient k ₄ of the fourth layer is 0.1 or less.
(Configuration 11)
The fourth layer is formed of a material consisting of silicon and oxygen, or a material consisting of one or more elements selected from metalloid elements and nonmetallic elements, and silicon and oxygen. 10. The mask blank according to 10.

(Configuration 12)
A phase shift mask provided with a phase shift film having a transfer pattern formed on a translucent substrate,
The phase shift film includes a structure in which a first layer, a second layer, and a third layer are stacked in this order from the translucent substrate side,
When the refractive indexes at the wavelengths of the exposure light of the ArF excimer laser of the first layer, the second layer, and the third layer are n ₁ , n ₂ , and n ₃ , respectively, n ₁ > n ₂ and n ₂ <n _Satisfying the relationship of ₃
When extinction coefficients at the wavelengths of the exposure light of the first layer, the second layer, and the third layer are k ₁ , k ₂ , and k ₃ , respectively, k ₁ <k ₂ and k ₂ > k ₃ Meet relationships,
When the film thicknesses of the first layer, the second layer, and the third layer are d ₁ , d ₂ , and d ₃ , respectively, the relationship of d ₁ <d ₃ and d ₂ <d ₃ is satisfied. Phase shift mask.

(Configuration 13)
Said third layer thickness d ₃ of the phase shift mask structure 12, wherein the at first layer 2 times or more the thickness d ₁ of the.

(Configuration 14)
The thickness d ₂ of the second layer, a phase shift mask according to the structure 12 or 13, characterized in that at 20nm or less.
(Configuration 15)
Refractive index _{n 1} of the first layer is 2.0 or more, the extinction coefficient _{k 1} of the first layer is 0.5 or less, the refractive index _{n 2} of the second layer is less than 2.0 The extinction coefficient k ₂ of the second layer is 1.0 or more, the refractive index n ₃ of the third layer is 2.0 or more, and the extinction coefficient k ₃ of the third layer is 0. The phase shift mask according to any one of Configurations 12 to 14, wherein the phase shift mask is 5 or less.

(Configuration 16)
The phase shift film has a function of transmitting the exposure light with a transmittance of 2% or more, and the exposure light transmitted through the phase shift film has passed through the air by the same distance as the thickness of the phase shift film. 16. The phase shift mask according to claim 12, wherein the phase shift mask has a function of generating a phase difference of not less than 150 degrees and not more than 200 degrees with the exposure light.
(Configuration 17)
The phase shift mask according to any one of Structures 12 to 16, wherein the first layer is provided in contact with the surface of the light-transmitting substrate.

(Configuration 18)
The first layer, the second layer, and the third layer are formed of a material composed of silicon and nitrogen, or a material composed of one or more elements selected from a semi-metallic element and a nonmetallic element, and silicon and nitrogen. 18. The phase shift mask according to any one of Configurations 12 to 17, wherein:
(Configuration 19)
19. The phase shift mask according to configuration 18, wherein the nitrogen content of the second layer is less than the nitrogen content of any of the first layer and the third layer.

(Configuration 20)
The phase shift film includes a fourth layer on the third layer,
When the refractive index in the wavelength of the exposure light of the fourth layer was _{n 4,} satisfies the n 1> _{n 4} and _n 3> _{n 4} relationship,
When the extinction coefficient at the wavelength of the exposure light of the fourth layer was k _4, k _1> according to any one of k ₄ and k _3> k constituting 12 to 19 and satisfying the relation of ₄ Phase shift mask.
(Configuration 21)
It said fourth layer refractive index n ₄ of is 1.8 or less, and a phase shift mask structure 20, wherein the fourth layer extinction coefficient k ₄ of is 0.1 or less.

(Configuration 22)
The fourth layer is formed of a material consisting of silicon and oxygen, or a material consisting of one or more elements selected from metalloid elements and nonmetallic elements, and silicon and oxygen. The phase shift mask according to 21.
(Configuration 23)
23. A method of manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the phase shift mask according to any one of Structures 12 to 22.

  The mask blank of the present invention includes a phase shift film on a light-transmitting substrate, and the phase shift film has a function of transmitting ArF excimer laser exposure light with a predetermined transmittance and an ArF excimer that transmits the function. It is possible to provide a mask blank including a phase shift film having a reduced back surface reflectance while also having a function of generating a predetermined phase difference with respect to laser exposure light.

It is sectional drawing which shows the structure of the mask blank in the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the mask blank in the 2nd Embodiment of this invention. It is a cross-sectional schematic diagram which shows the manufacturing process of the phase shift mask in the 1st and 2nd embodiment of this invention.

  Embodiments of the present invention will be described below. The inventors of the present application have a function of transmitting ArF excimer laser exposure light (hereinafter, simply referred to as exposure light) with a predetermined transmittance and a function of generating a predetermined phase difference in the phase shift film, while reflecting the back surface. We conducted intensive research on means to further reduce the rate.

  The stray light generated at the time of exposure to the transfer mask is such that part of the exposure light incident from the front surface (back surface) of the translucent substrate of the phase shift mask (the side where the phase shift film is not provided) is translucent substrate The light is reflected at the interface between the transparent substrate and the phase shift film, and is reflected again at the interface between the back surface of the light-transmitting substrate and the air, and is emitted from the area where there is no phase shift film on the front surface of the light-transmitting substrate It is considered a thing. In order to suppress the reflection of the bar code or alignment mark caused by this stray light, it is desired that the light intensity of the stray light with respect to the light intensity of the exposure light irradiated on the translucent substrate is 0.2% or less. In the phase shift mask, the light shielding band (laminated structure of the phase shift film and the light shielding film) provided in the outer peripheral region of the region where the transfer pattern is formed preferably has a transmittance of 0.2% or less. ing. With this transmittance, even if exposure light is transmitted, it is said that there is substantially no influence on the CD variation of the resist film on the semiconductor device.

  When the ArF excimer laser exposure light is exposed to the phase shift mask, when the exposure light is incident on the back surface of the translucent substrate from the air, the light reflected on the back surface of the translucent substrate is incident light. About 5% occurs (that is, the light intensity of the exposure light incident on the inside of the translucent substrate decreases by about 5%). Furthermore, when a part of the exposure light reflected at the interface between the translucent substrate and the phase shift film is reflected at the interface between the back surface of the translucent substrate and the air, a part of the light is not reflected. Emanates from the back surface. As a result of examining these points, in the state where only the phase shift film exists on the light-transmitting substrate, the light-transmitting substrate side (back surface side) reflectance (back surface reflectance) with respect to the exposure light is 9% or less. For example, the light intensity of stray light can be reduced to 0.2% or less, and it has been thought that reflection of a bar code or an alignment mark can be suppressed.

  When actually measuring the back surface reflectance of the phase shift film, the surface of the translucent substrate opposite to the side on which the phase shift film is provided (back surface) is irradiated with measurement light to reflect the reflected light. The intensity is measured, and the back surface reflectance is obtained from the light intensity of the reflected light. The light intensity of the measured reflected light is the light reflected at the interface between the air and the translucent substrate, and the measurement light that is incident on the translucent substrate without being reflected there is transmitted between the translucent substrate and the phase shift film. And at least light that is emitted into the air without being re-reflected at the interface between the back surface of the translucent substrate and the air (light that is less than 4% of the light incident on the interface). It becomes the light intensity of light. That is, the above-described back surface reflectance of 9% or less is a back surface reflectance obtained from light including reflected light other than light reflected at the interface between the light-transmitting substrate and the phase shift film.

Then, the inventor has a function of transmitting ArF excimer laser exposure light at a predetermined transmittance and a function of causing a predetermined phase difference, and a phase shift for realizing a back surface reflectance of 9% or less. The structure of the mask blank provided with the film was examined.
As a material for forming a conventional phase shift film, a material having a refractive index n as large as possible and an extinction coefficient k within a range that is neither too large nor too small is preferred. The conventional phase shift film mainly absorbs the exposure light of the ArF excimer laser inside the phase shift film so that the exposure light of the ArF excimer laser is transmitted at a predetermined transmittance, while the exposure of the ArF excimer laser passing therethrough is transmitted. This is because the design concept is to generate a predetermined phase difference with respect to light. The phase shift film having a single layer structure has a function required for the phase shift film (a function that causes a predetermined transmittance and phase difference with respect to the exposure light of the ArF excimer laser transmitted through the phase shift film) It is difficult to realize a back surface reflectance of 9% or less. Therefore, the present inventor has a function of transmitting a ArF excimer laser exposure light with a predetermined transmittance and a function of generating a predetermined phase difference in the entire layer by configuring the phase shift film with a plurality of layers. In addition, we studied to achieve a back surface reflectance of 9% or less. In order to reduce the back surface reflectance of the phase shift film with respect to the exposure light of the ArF excimer laser, the reflected light at the interface between the translucent substrate and the phase shift film and the reflected light at the interface between the layers constituting the phase shift film It is also necessary to use the interference effect.

As a result of considering these points, the phase shift film has a structure in which the first layer, the second layer, and the third layer are stacked in this order from the translucent substrate side, and the first layer at the wavelength of the ArF excimer laser exposure light, By adjusting the refractive indices n ₁ , n ₂ , n ₃ , extinction coefficients k ₁ , k ₂ , k ₃ and the film thicknesses d ₁ , d ₂ , d ₃ of the second layer and the third layer, ArF It has been found that a phase shift film having a back surface reflectance of 9% or less can be formed while having a predetermined transmittance and a predetermined phase difference with respect to the exposure light of the excimer laser. The present invention has been made by the above-mentioned earnest studies.

FIG. 1 is a cross-sectional view showing a configuration of a mask blank 100 according to the first embodiment of the present invention. A mask blank 100 of the present invention shown in FIG. 1 has a structure in which a phase shift film 2, a light shielding film 3, and a hard mask film 4 are laminated in this order on a translucent substrate 1.
The translucent substrate 1 can be formed of quartz glass, aluminosilicate glass, soda lime glass, low thermal expansion glass (SiO ₂ —TiO ₂ glass or the like), in addition to synthetic quartz glass. Among these, synthetic quartz glass has a high transmittance with respect to ArF excimer laser light, and is particularly preferable as a material for forming the translucent substrate 1 of the mask blank. The refractive index n at the wavelength (about 193 nm) of the exposure light of the ArF excimer laser, which is a material forming the translucent substrate 1, is preferably 1.5 or more and 1.6 or less, and 1.52 or more and 1.59 or less. More preferably, it is 1.54 or more and 1.58 or less.

  In order to produce a sufficient phase shift effect between the exposure light transmitted through the phase shift film 2 and the exposure light transmitted through the air in the phase shift film 2, the transmittance of the ArF excimer laser with respect to the exposure light Is preferably 2% or more. The transmittance of the phase shift film 2 with respect to exposure light is preferably 3% or more, and more preferably 4% or more. On the other hand, the transmittance of the phase shift film 2 with respect to the exposure light is preferably 15% or less, and more preferably 14% or less.

  In order to obtain an appropriate phase shift effect, the phase shift film 2 is formed between the transmitted light of the ArF excimer laser and the light that has passed through the air by the same distance as the thickness of the phase shift film 2. It is preferable that the phase difference is adjusted to be in the range of 150 ° to 200 °. The lower limit value of the phase difference in the phase shift film 2 is preferably 155 degrees or more, and more preferably 160 degrees or more. On the other hand, the upper limit value of the phase difference in the phase shift film 2 is preferably 190 degrees or less.

  In the state where only the phase shift film 2 exists on the translucent substrate 1, the phase shift film 2 preferably has a back surface reflectance of at least 9% or less with respect to the exposure light of the ArF excimer laser.

The phase shift film 2 has a structure in which a first layer 21, a second layer 22, and a third layer 23 are laminated from the translucent substrate 1 side. The entire phase shift film 2 needs to satisfy at least the above-described conditions of transmittance, phase difference, and back surface reflectance. In order for the phase shift film 2 to satisfy the above conditions, the refractive indexes of the first layer 21, the second layer 22, and the third layer 23 at the wavelength of the exposure light of the ArF excimer laser are respectively n ₁ , n ₂ , n ₃ and When satisfying the relationship of n ₁ > n ₂ and n ₂ <n ₃ , the extinction coefficients at the wavelengths of the exposure light of the first layer, the second layer, and the third layer are respectively k ₁ , k ₂ , k _3. The present inventors have found that it is necessary to satisfy the relationship of k ₁ <k ₂ and k ₂ > k ₃ .
In addition, the refractive index n ₁ of the first layer 21 is preferably 2.0 or more, and more preferably 2.1 or more. Further, the refractive index n ₁ of the first layer 21 is preferably 3.0 or less, and more preferably 2.8 or less. The extinction coefficient k ₁ of the first layer 21 is preferably 0.5 or less, and more preferably 0.4 or less. Further, the extinction coefficient k ₁ of the first layer 21 is preferably 0.1 or more, and more preferably 0.2 or more. Note that the refractive index n ₁ and the extinction coefficient k ₁ of the first layer 21 are values derived by regarding the entire first layer 21 as one optically uniform layer.

In order for the phase shift film 2 to satisfy the above conditions, the refractive index n ₂ of the second layer 22 is preferably less than 2.0, and more preferably 1.9 or less. Further, the refractive index n ₂ of the second layer 22 is preferably 1.0 or more, and more preferably 1.2 or more. Further, the extinction coefficient _{k 2} of the second layer 22 is preferably 1.0 or more, and more preferably 1.2 or more. Further, the extinction coefficient _{k 2} of the second layer 22 is preferable to be 2.2 or less, more preferably 2.0 or less. The refractive index n ₂ and extinction coefficient k ₂ of the second layer 22 are values derived by regarding the entire second layer 22 as one optically uniform layer.
In order for the phase shift film 2 to satisfy the above condition, the refractive index n ₃ of the third layer 23 is preferably 2.0 or more, and more preferably 2.1 or more. Further, the refractive index n ₃ of the third layer 23 is preferably 3.0 or less, and more preferably 2.8 or less. The extinction coefficient k ₃ of the third layer 23 is preferably 0.5 or less, and more preferably 0.4 or less. The extinction coefficient k ₃ of the third layer 23 is preferably 0.1 or more, and more preferably 0.2 or more. The refractive index n ₃ and the extinction coefficient k ₃ of the third layer 23 are values derived by regarding the entire third layer 23 as one optically uniform layer.

  The refractive index n and extinction coefficient k of the thin film including the phase shift film 2 are not determined only by the composition of the thin film. The film density and crystal state of the thin film are factors that influence the refractive index n and the extinction coefficient k. For this reason, various conditions when forming a thin film by reactive sputtering are adjusted, and the thin film is formed so as to have a desired refractive index n and extinction coefficient k. In order to make the first layer 21, the second layer 22, and the third layer 23 within the ranges of the refractive index n and the extinction coefficient k, noble gas and reactive gas ( It is not limited to adjusting the ratio of the mixed gas of oxygen gas, nitrogen gas, etc. There are a variety of positional relationships such as the pressure in the film forming chamber during film formation by reactive sputtering, the power applied to the sputtering target, and the distance between the target and the translucent substrate 1. These film forming conditions are unique to the film forming apparatus, and are appropriately adjusted so that the formed first layer 21, second layer 22, and third layer 23 have a desired refractive index n and extinction coefficient k. It is what is done.

In order for the phase shift film 2 to satisfy the above conditions, in addition to the optical characteristics of the first layer 21, the second layer 22, and the third layer 23, the first layer 21, the second layer 22, and the third layer 23 are used. When d ₁ , d ₂ , and d ₃ are set to d ₁ , d ₂ , and d ₃ , respectively, it is necessary to satisfy at least the relationship of d ₁ <d ₃ and d ₂ <d ₃

  The thickness of the first layer 21 is preferably 20 nm or less, and more preferably 18 nm or less. Further, the thickness of the first layer 21 is preferably 3 nm or more, and more preferably 5 nm or more.

  The thickness of the second layer 22 is preferably 20 nm or less, and more preferably 18 nm or less. Further, the thickness of the second layer 22 is preferably 2 nm or more, and more preferably 3 nm or more.

The first layer 21 has a higher rate of contribution to the adjustment of the back surface reflectance of the phase shift film 2 than the other two layers. Further, the ratio of the second layer 22 that contributes to the adjustment of the transmittance of the phase shift film 2 is higher than that of the other two layers. For this reason, the design freedom of the film thicknesses of the first layer 21 and the second layer 22 is relatively narrow. The third layer 23 is required to contribute to adjustment for having a predetermined phase difference for which the phase shift film 2 is required, and is desirably thicker than the other two layers. Thickness _{d 3} of the third layer 23 is preferably first layer 21 is more than twice the thickness _{d 1,} and more preferable to be 2.2 times or more, further When it is 2.5 times or more preferable. Further, the film thickness d ₃ of the third layer 23 is more preferably 5 times or less than the film thickness d ₁ of the first layer 21. The thickness of the third layer 23 is preferably 60 nm or less, and more preferably 50 nm or less. The thickness of the third layer 23 is preferably larger than 20 nm, more preferably 25 nm or more.

  The first layer 21, the second layer 22, and the third layer 23 are formed of a material composed of silicon and nitrogen, or a material composed of one or more elements selected from metalloid elements and nonmetallic elements, and silicon and nitrogen. It is preferable. Among these metalloid elements, it is preferable to include one or more elements selected from boron, germanium, antimony, and tellurium because it can be expected to increase the conductivity of silicon used as a sputtering target. Among these nonmetallic elements, it is preferable to contain one or more elements selected from nitrogen, carbon, fluorine and hydrogen. This nonmetallic element includes noble gases such as helium (He), argon (Ar), krypton (Kr), and xenon (Xe).

The second layer 22 preferably has a lower nitrogen content than either the first layer 21 or the third layer 23. The nitrogen content in the material forming the second layer 22 is preferably 40 atomic percent or less, and more preferably 35 atomic percent or less. The second layer 22 needs to contribute to the transmittance of the phase shift film 2, but increasing the nitrogen content leads to an increase in transmittance. The first layer 21 and the third layer 23 are preferably 50 atomic% or more, more preferably 55 atomic% or more, and are composed of Si ₃ N ₄ which is a stoichiometrically stable material. More preferably. The first layer and the third layer are preferably formed of a material having a high refractive index, but the refractive index can be increased by increasing the nitrogen content.

  The first layer 21 is preferably provided in contact with the surface of the translucent substrate 1. The configuration in which the first layer 21 is in contact with the surface of the translucent substrate 1 has a back surface reflectance generated by the laminated structure of the first layer 21, the second layer, and the third layer 23 of the phase shift film 2. This is because a reduction effect can be obtained more. An etching stopper film may be provided between the translucent substrate 1 and the phase shift film 2 if the influence on the effect of reducing the back surface reflectance of the phase shift film 2 is very small. In this case, the thickness of the etching stopper film needs to be 10 nm or less, preferably 7 nm or less, and more preferably 5 nm or less. From the viewpoint of effectively functioning as an etching stopper, the thickness of the etching stopper film needs to be 3 nm or more. The extinction coefficient k of the material forming the etching stopper film needs to be less than 0.1, preferably 0.05 or less, and more preferably 0.01 or less. In this case, the refractive index n of the material forming the etching stopper film is required to be at least 1.9 or less, and is preferably 1.7 or less. The refractive index n of the material forming the etching stopper film is preferably 1.55 or more. The etching stopper film is preferably formed of a material containing silicon, aluminum, and oxygen.

  It is preferable that the material forming the first layer 21 and the second layer 22 and the material forming the third layer 23 excluding the oxidized surface layer portion are both composed of the same element. The first layer 21, the second layer 22, and the third layer 23 are patterned by dry etching using the same etching gas. For this reason, it is desirable to etch the first layer 21, the second layer 22, and the third layer 23 in the same etching chamber. If the elements constituting each material forming the first layer 21, the second layer 22, and the third layer 23 are the same, dry etching is performed to the first layer 21, the second layer 22, and the third layer 23. The environmental change in the etching chamber when the object changes can be reduced.

  The first layer 21, the second layer 22, and the third layer 23 in the phase shift film 2 are formed by sputtering, but any sputtering such as DC sputtering, RF sputtering, and ion beam sputtering is applicable. In consideration of the deposition rate, it is preferable to apply DC sputtering. In the case of using a target with low conductivity, it is preferable to apply RF sputtering or ion beam sputtering, but it is more preferable to apply RF sputtering in consideration of the film formation rate.

  The mask blank 100 includes a light shielding film 3 on the phase shift film 2. In general, in a binary mask, the outer peripheral area of a transfer pattern formation area (transfer pattern formation area) is affected by exposure light transmitted through the outer peripheral area when exposed and transferred to a resist film on a semiconductor wafer using an exposure apparatus. Therefore, it is required to secure an optical density (OD) of a predetermined value or higher so that the resist film does not receive the resist. This also applies to the phase shift mask. Usually, it is preferable that OD is 2.7 or more in the outer peripheral region of the transfer mask including the phase shift mask. The phase shift film 2 has a function of transmitting exposure light with a predetermined transmittance, and it is difficult to ensure a predetermined optical density with the phase shift film 2 alone. For this reason, it is necessary to laminate the light shielding film 3 on the phase shift film 2 at the stage of manufacturing the mask blank 100 in order to ensure an insufficient optical density. With such a mask blank 100 configuration, the light shielding film 3 in the region (basically the transfer pattern forming region) where the phase shift effect is used is removed in the course of manufacturing the phase shift mask 200 (see FIG. 3). By doing so, it is possible to manufacture the phase shift mask 200 in which an optical density of a predetermined value is secured in the outer peripheral region.

  The light shielding film 3 can be applied to either a single layer structure or a laminated structure of two or more layers. In addition, each layer of the light-shielding film 3 having a single-layer structure and the light-shielding film 3 having a laminated structure of two or more layers has a composition in the layer thickness direction even if the layers have almost the same composition in the film thickness direction. An inclined configuration may be used.

  The mask blank 100 in the form shown in FIG. 1 has a configuration in which the light shielding film 3 is laminated on the phase shift film 2 without interposing another film. For the light shielding film 3 in this configuration, it is necessary to apply a material having sufficient etching selectivity with respect to an etching gas used when a pattern is formed on the phase shift film 2. In this case, the light-shielding film 3 is preferably formed of a material containing chromium. Examples of the material containing chromium that forms the light shielding film 3 include a material containing one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine in addition to chromium metal.

  In general, a chromium-based material is etched with a mixed gas of a chlorine-based gas and an oxygen gas, but chromium metal does not have a high etching rate with respect to this etching gas. In consideration of increasing the etching rate of the mixed gas of chlorine-based gas and oxygen gas with respect to the etching gas, the material for forming the light shielding film 3 is one or more elements selected from chromium, oxygen, nitrogen, carbon, boron and fluorine. A material containing is preferred. Moreover, you may make the material containing chromium which forms the light shielding film 3 contain one or more elements among molybdenum, indium, and tin. By including one or more elements of molybdenum, indium and tin, the etching rate with respect to the mixed gas of chlorine gas and oxygen gas can be further increased.

  Further, the light-shielding film 3 may be formed of a material containing a transition metal and silicon as long as the etching selectivity for dry etching can be obtained with the material forming the third layer 23 (particularly the surface layer portion). . This is because a material containing a transition metal and silicon has a high light shielding performance, and the thickness of the light shielding film 3 can be reduced. As transition metals to be contained in the light shielding film 3, molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium (Hf), nickel (Ni), vanadium (V) , Zirconium (Zr), ruthenium (Ru), rhodium (Rh), zinc (Zn), niobium (Nb), palladium (Pd), and any one metal or an alloy of these metals. Examples of the metal element other than the transition metal element contained in the light shielding film 3 include aluminum (Al), indium (In), tin (Sn), and gallium (Ga).

  On the other hand, as a mask blank 100 according to another embodiment, a light shielding film 3 having a structure in which a layer made of a material containing chromium and a layer made of a material containing transition metal and silicon are laminated in this order from the phase shift film 2 side. May be. The specific matters of the material containing chromium and the material containing transition metal and silicon in this case are the same as those of the light shielding film 3 described above.

  The mask blank 100 preferably has a back surface reflectance of 9% or less with respect to the exposure light of the ArF excimer laser in a state where the phase shift film 2 and the light shielding film 3 are laminated.

  In the mask blank 100, it is preferable that a hard mask film 4 formed of a material having etching selectivity with respect to an etching gas used when etching the light shielding film 3 is further laminated on the light shielding film 3. Since the hard mask film 4 is basically not restricted by the optical density, the thickness of the hard mask film 4 can be made much thinner than the thickness of the light shielding film 3. The resist film made of an organic material is sufficient to have a thickness sufficient to function as an etching mask until dry etching for forming a pattern on the hard mask film 4 is completed. The thickness can be greatly reduced. Thinning the resist film is effective in improving resist resolution and preventing pattern collapse, and is extremely important in meeting the demand for miniaturization.

When the light shielding film 3 is formed of a material containing chromium, the hard mask film 4 is preferably formed of a material containing silicon. Since the hard mask film 4 in this case tends to have low adhesion to the organic material resist film, the surface of the hard mask film 4 is subjected to HMDS (Hexamethyldisilazane) treatment to improve surface adhesion. It is preferable. In this case, the hard mask film 4 is more preferably formed of SiO ₂ , SiN, SiON or the like.

  In addition to the above, a material containing tantalum is also applicable as the material of the hard mask film 4 when the light shielding film 3 is formed of a material containing chromium. Examples of the material containing tantalum in this case include a material in which tantalum contains one or more elements selected from nitrogen, oxygen, boron, and carbon in addition to tantalum metal. Examples thereof include Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, TaBOCN, and the like. Moreover, when the light shielding film 3 is formed of a material containing silicon, the hard mask film 4 is preferably formed of the material containing chromium.

  In the mask blank 100, it is preferable that a resist film of an organic material is formed with a thickness of 100 nm or less in contact with the surface of the hard mask film 4. In the case of a fine pattern corresponding to the DRAM hp32 nm generation, a transfer pattern (phase shift pattern) to be formed on the hard mask film 4 may be provided with SRAF (Sub-Resolution Assist Feature) having a line width of 40 nm. However, even in this case, since the cross-sectional aspect ratio of the resist pattern can be reduced to 1: 2.5, it is possible to suppress the resist pattern from collapsing or detaching during development or rinsing of the resist film. The resist film is more preferably 80 nm or less in thickness.

  FIG. 2 is a cross-sectional view showing a configuration of a mask blank 110 according to the second embodiment of the present invention. In the mask blank 110 according to the present embodiment, the phase shift film 2 has a structure in which the first layer 21, the second layer 22, the third layer 23, and the fourth layer 24 are laminated from the translucent substrate 1 side. About the 1st layer 21, the 2nd layer 22, and the 3rd layer 23, since a suitable refractive index, an extinction coefficient, and a film thickness are as having described in 1st Embodiment, description is abbreviate | omitted. The configurations of the translucent substrate 1, the light shielding film 3, and the hard mask film 4 are also as described in the first embodiment.

The fourth layer 24 itself has little influence on the back surface reflectance, but when the refractive index at the wavelength of the exposure light of the ArF excimer laser of the fourth layer 24 is n ₄ , n ₁ > n ₄ and n ₃ > satisfy the relation of _{n 4,} when the extinction coefficient was _{k 4} at the wavelength of the exposure light ArF excimer laser of the fourth layer _24, satisfies the relationship of k 1> _{k 4} and _k 3> _{k 4} It is preferable. It is more preferable that the relationship of n ₂ > n ₄ is also satisfied. The fourth layer 24 preferably has a refractive index n ₄ of 1.8 or less, and more preferably 1.7 or less. The fourth layer 24 preferably has a refractive index n ₄ of 1.5 or more, and more preferably 1.55 or more. On the other hand, the fourth layer 24 is preferably the extinction coefficient _{k 4} is 0.1 or less, more preferably 0.05 or less.

  The fourth layer 24 is preferably formed of a material composed of silicon and oxygen, or a material composed of one or more elements selected from a metalloid element and a nonmetallic element, and silicon and oxygen. By forming the fourth layer 24 with such a material, it is possible to suppress the occurrence of haze that is likely to occur in a silicon-containing film having a high nitrogen content. Further, the thickness of the fourth layer 24 is preferably 15 nm or less, and more preferably 10 nm or less. Further, the thickness of the fourth layer 24 is preferably 1 nm or more, and more preferably 2 nm or more.

  FIG. 3 shows the phase shift masks 200 and 210 according to the first and second embodiments of the present invention manufactured from the mask blanks 100 and 110 according to the first and second embodiments and the manufacturing process thereof. As shown in FIG. 3G, in the phase shift masks 200 and 210, the phase shift pattern 2a as a transfer pattern is formed on the phase shift film 2 of the mask blanks 100 and 110, and the light shielding pattern is formed on the light shielding film 3. 3b is formed. In the case where the hard mask film 4 is provided on the mask blanks 100 and 110, the hard mask film 4 is removed while the phase shift masks 200 and 210 are being formed.

  The method of manufacturing the phase shift masks 200 and 210 according to the first and second embodiments of the present invention uses the mask blanks 100 and 110, and forms a transfer pattern on the light shielding film 3 by dry etching. And a step of forming a transfer pattern on the phase shift film 2 by dry etching using the light shielding film 3 having a transfer pattern as a mask, and a dry etching using the resist film (second resist pattern) 6b having a light shielding pattern as a mask. And a step of forming a light shielding pattern 3b on the light shielding film 3. Hereinafter, according to the manufacturing process shown in FIG. 3, the manufacturing method of the phase shift masks 200 and 210 of the present invention will be described. Here, a method of manufacturing the phase shift masks 200 and 210 using the mask blanks 100 and 110 in which the hard mask film 4 is laminated on the light shielding film 3 will be described. The case where a material containing chromium is applied to the light shielding film 3 and a material containing silicon is applied to the hard mask film 4 will be described.

  First, a resist film is formed by spin coating in contact with the hard mask film 4 in the mask blanks 100 and 110. Next, a first pattern, which is a transfer pattern (phase shift pattern) to be formed on the phase shift film 2, is exposed and drawn on the resist film with an electron beam, and a predetermined process such as a development process is further performed. A first resist pattern 5a having a shift pattern was formed (see FIG. 3A). Subsequently, dry etching using a fluorine-based gas was performed using the first resist pattern 5a as a mask to form a first pattern (hard mask pattern 4a) on the hard mask film 4 (see FIG. 3B). .

  Next, after removing the resist pattern 5a, dry etching using a mixed gas of chlorine gas and oxygen gas is performed using the hard mask pattern 4a as a mask, and the first pattern (light shielding pattern 3a) is formed on the light shielding film 3. (See FIG. 3C). Subsequently, dry etching using a fluorine-based gas is performed using the light-shielding pattern 3a as a mask to form a first pattern (phase shift pattern 2a) on the phase shift film 2, and the hard mask pattern 4a is removed (FIG. 5). 3 (d)).

  Next, a resist film was formed on the mask blanks 100 and 110 by a spin coating method. Next, a second pattern, which is a pattern to be formed on the light-shielding film 3 (light-shielding pattern), is exposed and drawn on the resist film with an electron beam, and further subjected to a predetermined process such as a development process to have a light-shielding pattern A second resist pattern 6b was formed (see FIG. 3E). Subsequently, dry etching using a mixed gas of chlorine-based gas and oxygen gas is performed using the second resist pattern 6b as a mask to form a second pattern (light-shielding pattern 3b) on the light-shielding film 3 (FIG. 3 ( f)). Further, the second resist pattern 6b was removed, and after a predetermined process such as cleaning, phase shift masks 200 and 210 were obtained (see FIG. 3G).

The chlorine-based gas used in the dry etching is not particularly limited as long as it contains Cl. For example, Cl ₂ , SiCl ₂ , CHCl ₃ , CH ₂ Cl ₂ , CCl ₄ , BCl _{3 and the} like can be mentioned. Further, the fluorine gas used in the dry etching is not particularly limited as long as F is contained. For _{example, CHF 3, CF 4, C} 2 F 6, C 4 F 8, SF 6 and the like. In particular, since the fluorine-based gas not containing C has a relatively low etching rate with respect to the glass substrate, damage to the glass substrate can be further reduced.

  The phase shift masks 200 and 210 of the present invention are produced using the mask blanks 100 and 110 described above. Therefore, the phase shift film 2 (phase shift pattern 2a) on which the transfer pattern is formed has an ArF excimer laser transmittance of 2% or more for the exposure light, and the exposure light and the phase shift pattern transmitted through the phase shift pattern 2a. The phase difference between the exposure light passing through the air by the same distance as the thickness of 2a is in the range of 150 degrees to 200 degrees. Further, the phase shift masks 200 and 210 have a back surface reflectance of 9% in the region of the phase shift pattern 2a where the light shielding pattern 3b is not laminated (the region on the translucent substrate 1 where only the phase shift pattern 2a exists). It is as follows. Thereby, when exposure transfer is performed on a transfer target (such as a resist film on a semiconductor wafer) using the phase shift mask 200, the influence of the stray light on the exposure transfer image can be suppressed.

  The semiconductor device manufacturing method of the present invention is characterized in that the transfer pattern is exposed and transferred onto a resist film on a semiconductor substrate using the phase shift masks 200 and 210 described above. The phase shift masks 200 and 210 have a function of transmitting ArF excimer laser exposure light with a predetermined transmittance and a function of generating a predetermined phase difference with respect to the transmitted ArF excimer laser exposure light. The reflectance is 9% or less, which is greatly reduced compared to the conventional one. For this reason, the phase shift masks 200 and 210 are set in an exposure apparatus, and exposure light of an ArF excimer laser is irradiated from the translucent substrate 1 side of the phase shift masks 200 and 210 to transfer a transfer object (on a semiconductor wafer). Even if an exposure transfer process to a resist film or the like is performed, the reflection of the barcode or alignment mark formed on the phase shift masks 200 and 210 on the transfer object can be suppressed, and the transfer object can be accurately performed. A desired pattern can be transferred.

Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples.
Example 1
[Manufacture of mask blanks]
A translucent substrate 1 made of synthetic quartz glass having a main surface dimension of about 152 mm × about 152 mm and a thickness of about 6.35 mm was prepared. The translucent substrate 1 has its end face and main surface polished to a predetermined surface roughness and then subjected to a predetermined cleaning process and drying process. When the optical characteristics of the translucent substrate 1 were measured, the refractive index n was 1.556 and the extinction coefficient k was 0.00.

Next, the translucent substrate 1 is installed in a single-wafer RF sputtering apparatus, and RF sputtering using a silicon (Si) target and a mixed gas of argon (Ar) gas and nitrogen (N ₂ ) as a sputtering gas. The first layer 21 (SiN film Si: N = 43 atomic%: 57 atomic%) of the phase shift film 2 made of silicon and nitrogen was formed in contact with the surface of the translucent substrate 1 to a thickness of 12 nm. Subsequently, the first layer 21 is made of silicon and nitrogen by reactive sputtering (RF sputtering) using a silicon (Si) target and using a mixed gas of argon (Ar) and nitrogen (N ₂ ) as a sputtering gas. A second layer 22 of the phase shift film 2 (SiN film Si: N = 68 atomic%: 32 atomic%) was formed with a thickness of 15 nm. Subsequently, silicon and nitrogen are formed on the second layer 22 by reactive sputtering (RF sputtering) using a silicon (Si) target and using a mixed gas of argon (Ar) and nitrogen (N ₂ ) as a sputtering gas. A third layer 23 (SiN film Si: N = 43 atomic%: 57 atomic%) of the phase shift film 2 was formed with a thickness of 42 nm. According to the above procedure, the phase shift film 2 in which the first layer 21, the second layer 22, and the third layer 23 were laminated in contact with the surface of the translucent substrate 1 was formed with a thickness of 69 nm. In the phase shift film 2, the thickness of the third layer 23 is 3.5 times the thickness of the first layer 21. The compositions of the first layer 21, the second layer 22, and the third layer 23 are results obtained by measurement by X-ray photoelectron spectroscopy (XPS). The same applies to other films.

Next, using a phase shift amount measuring device (MPM193 manufactured by Lasertec Corporation), the transmittance and phase difference of the phase shift film 2 with respect to the light of the exposure light wavelength (wavelength 193 nm) of the ArF excimer laser were measured. The rate was 6.2%, and the phase difference was 181.8 degrees (deg). Further, when the optical characteristics of the first layer 21, the second layer 22, and the third layer 23 of the phase shift film 2 were measured with a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam), the first layer was measured. 21 has a refractive index n ₁ of 2.595 and an extinction coefficient k ₁ of 0.357, and the second layer 22 has a refractive index n ₂ of 1.648 and an extinction coefficient k ₂ of 1.861, The third layer 23 had a refractive index n ₃ of 2.595 and an extinction coefficient k ₃ of 0.357. The back surface reflectance of the phase shift film 2 with respect to the light having the wavelength of the exposure light of the ArF excimer laser was 3.8%, which was less than 9%.

Next, the translucent substrate 1 on which the phase shift film 2 is formed is installed in a single-wafer DC sputtering apparatus, and using a chromium (Cr) target, argon (Ar), carbon dioxide (CO ₂ ), nitrogen ( A light shielding film 3 (CrOCN film Cr: O: C: N = 55 atoms) made of CrOCN on the phase shift film 2 by reactive sputtering (DC sputtering) using a mixed gas of N ₂ ) and helium (He) as a sputtering gas. %: 22 atomic%: 12 atomic%: 11 atomic%) was formed with a thickness of 43 nm. In the state where the phase shift film 2 and the light shielding film 3 are laminated on the translucent substrate 1, the back surface reflectance with respect to the light having the wavelength of the exposure light of the ArF excimer laser is 4.7%, which is less than 9%. It was. The optical density (OD) of light having a wavelength of 193 nm in the laminated structure of the phase shift film 2 and the light shielding film 3 was measured and found to be 3.0 or more. Further, another light-transmitting substrate 1 was prepared, and only the light-shielding film 3 was formed under the same film-forming conditions. When the optical characteristics of the light-shielding film 3 were measured with the spectroscopic ellipsometer, the refractive index n was 1. 92 and the extinction coefficient k was 1.50.

Next, the translucent substrate 1 on which the phase shift film 2 and the light-shielding film 3 are laminated is placed in a single wafer RF sputtering apparatus, and argon (Ar) gas is sputtered using a silicon dioxide (SiO ₂ ) target. A hard mask film 4 made of silicon and oxygen was formed to a thickness of 5 nm on the light shielding film 3 by RF sputtering using gas. By the above procedure, a mask blank 100 having a structure in which the phase shift film 2, the light shielding film 3, and the hard mask film 4 having a three-layer structure were laminated on the light-transmitting substrate 1 was manufactured.

[Manufacture of phase shift mask]
Next, using the mask blank 100 of Example 1, the phase shift mask 200 of Example 1 was produced according to the following procedure. First, the surface of the hard mask film 4 was subjected to HMDS treatment. Subsequently, a resist film made of a chemically amplified resist for electron beam drawing with a film thickness of 80 nm was formed in contact with the surface of the hard mask film 4 by spin coating. Next, a first pattern which is a phase shift pattern to be formed on the phase shift film 2 is drawn on the resist film with an electron beam, a predetermined development process and a cleaning process are performed, and a first pattern having the first pattern is formed. 1 resist pattern 5a was formed (see FIG. 3A). At this time, a pattern having a shape corresponding to a barcode or an alignment mark was also formed in the first resist pattern 5a outside the pattern formation region.

Next, dry etching using CF ₄ gas was performed using the first resist pattern 5a as a mask to form a first pattern (hard mask pattern 4a) on the hard mask film 4 (see FIG. 3B). . At this time, a pattern having a shape corresponding to a barcode or an alignment mark was also formed on the hard mask film 4 outside the pattern formation region. Thereafter, the first resist pattern 5a was removed.

Subsequently, using the hard mask pattern 4a as a mask, dry etching using a mixed gas of chlorine and oxygen (gas flow ratio Cl ₂ : O ₂ = 10: 1) is performed, and the first pattern (light shielding pattern) is formed on the light shielding film 3. 3a) was formed (see FIG. 3 (c)). At this time, a pattern having a shape corresponding to the barcode or the alignment mark was also formed on the light shielding film 3 outside the pattern formation region. Next, using the light shielding pattern 3a as a mask, dry etching using fluorine-based gas (SF ₆ + He) is performed to form a first pattern (phase shift pattern 2a) on the phase shift film 2, and at the same time, a hard mask pattern 4a was removed (see FIG. 3 (d)). At this time, a pattern having a shape corresponding to the barcode or the alignment mark was also formed on the phase shift film 2 outside the pattern formation region.

Next, a resist film made of a chemically amplified resist for electron beam lithography was formed on the light-shielding pattern 3a with a film thickness of 150 nm by spin coating. Next, a second pattern, which is a pattern (light-shielding pattern) to be formed on the light-shielding film, is exposed and drawn on the resist film, and further subjected to a predetermined process such as a development process, whereby the second resist having the light-shielding pattern A pattern 6b was formed (see FIG. 3E). Subsequently, dry etching using a mixed gas of chlorine and oxygen (gas flow ratio Cl ₂ : O ₂ = 4: 1) is performed using the second resist pattern 6b as a mask, and the second pattern ( A light shielding pattern 3b) was formed (see FIG. 3F). Further, the second resist pattern 6b was removed, and a predetermined process such as cleaning was performed to obtain a phase shift mask 200 (see FIG. 3G).

  For this phase shift mask 200, an exposure transfer image was simulated when AIMS 193 (manufactured by Carl Zeiss) was exposed and transferred to a resist film on a semiconductor device with ArF excimer laser exposure light. When the exposure transfer image obtained by this simulation was verified, the design specifications were sufficiently satisfied. Further, no CD variation due to reflection of a barcode or an alignment mark was observed in the exposure transfer image. From the above, even if the phase shift mask 200 manufactured from the mask blank of Example 1 is set in an exposure apparatus and subjected to exposure transfer with exposure light of an ArF excimer laser, it is applied to the resist film on the semiconductor device. It can be said that exposure transfer can be performed with high accuracy.

(Example 2)
[Manufacture of mask blanks]
The mask blank 110 of Example 2 was manufactured in the same procedure as Example 1 except for the phase shift film 2. In the phase shift film 2 of Example 2, the thicknesses of the first layer 21, the second layer 22, and the third layer 23 are changed, and a fourth layer 24 is formed on the third layer 23. Specifically, the translucent substrate 1 is installed in a single wafer RF sputtering apparatus, a silicon (Si) target is used, and a mixed gas of argon (Ar) and nitrogen (N ₂ ) is used as a sputtering gas. By sputtering (RF sputtering), the first layer 21 (SiN film Si: N = 43 atomic%: 57 atomic%) of the phase shift film 2 made of silicon and nitrogen in contact with the surface of the translucent substrate 1 is 14 nm thick. Formed. Subsequently, the first layer 21 is made of silicon and nitrogen by reactive sputtering (RF sputtering) using a silicon (Si) target and using a mixed gas of argon (Ar) and nitrogen (N ₂ ) as a sputtering gas. A second layer 22 of the phase shift film 2 (SiN film Si: N = 68 atomic%: 32 atomic%) was formed with a thickness of 8 nm. Subsequently, silicon and nitrogen are formed on the second layer 22 by reactive sputtering (RF sputtering) using a silicon (Si) target and using a mixed gas of argon (Ar) and nitrogen (N ₂ ) as a sputtering gas. A third layer 23 (SiN film Si: N = 43 atomic%: 57 atomic%) of the phase shift film 2 was formed with a thickness of 43 nm. Subsequently, silicon and oxygen are formed on the third layer 23 by reactive sputtering (RF sputtering) using a silicon (Si) target and using a mixed gas of argon (Ar) and oxygen (O ₂ ) as a sputtering gas. A fourth layer 24 (SiO film Si: O = 33 atomic%: 67 atomic%) of the phase shift film 2 was formed with a thickness of 3 nm. By the above procedure, the phase shift film 2 in which the first layer 21, the second layer 22, the third layer 23, and the fourth layer 24 were laminated in contact with the surface of the translucent substrate 1 was formed with a thickness of 68 nm. In the phase shift film 2, the thickness of the third layer 23 is 3.07 times the thickness of the first layer 21.

When the transmittance and phase difference of the ArF excimer laser exposure light wavelength (wavelength 193 nm) of the phase shift film 2 were measured using the phase shift amount measuring apparatus, the transmittance was 11.6%. The phase difference was 183.0 degrees (deg). Further, when the optical characteristics of the first layer 21, the second layer 22, the third layer 23, and the fourth layer 24 of the phase shift film 2 were measured with the spectroscopic ellipsometer, the first layer 21 had a refractive index n _1. Is 2.595, the extinction coefficient k ₁ is 0.357, the second layer 22 has a refractive index n ₂ of 1.648, an extinction coefficient k ₂ of 1.861, and the third layer 23 The refractive index n ₃ was 2.595 and the extinction coefficient k ₃ was 0.357, and the fourth layer 24 had a refractive index n ₄ of 1.590 and an extinction coefficient k ₄ of 0.000. The back surface reflectance (reflectance on the translucent substrate 1 side) of the phase shift film 2 with respect to the light having the wavelength of the ArF excimer laser exposure light was 7.6%, which was less than 9%.

  Through the above procedure, the phase shift film 2, the light shielding film 3, and the hard mask film 4 including the first layer 21, the second layer 22, the third layer 23, and the fourth layer 24 are laminated on the light transmitting substrate 1. A mask blank 110 of Example 2 having the above structure was manufactured. The mask blank 110 of Example 2 has a back surface reflectance (translucency) with respect to light having the wavelength of the exposure light of the ArF excimer laser in a state where the phase shift film 2 and the light shielding film 3 are laminated on the translucent substrate 1. The reflectance on the substrate 1 side) was 7.9%, which was less than 9%. The optical density (OD) of light having a wavelength of 193 nm in the laminated structure of the phase shift film 2 and the light shielding film 3 was measured and found to be 3.0 or more.

[Manufacture of phase shift mask]
Next, using the mask blank 110 of Example 2, the phase shift mask 210 of Example 2 was produced in the same procedure as in Example 1.

  For this phase shift mask 210, an exposure transfer image was simulated when AIMS 193 (manufactured by Carl Zeiss) was exposed and transferred to a resist film on a semiconductor device with ArF excimer laser exposure light. When the exposure transfer image obtained by this simulation was verified, the design specifications were sufficiently satisfied. Further, no CD variation due to reflection of a barcode or an alignment mark was observed in the exposure transfer image. From the above, even if the phase shift mask 210 manufactured from the mask blank of Example 2 is set in an exposure apparatus and subjected to exposure transfer with exposure light of an ArF excimer laser, it is applied to the resist film on the semiconductor device. It can be said that exposure transfer can be performed with high accuracy.

(Comparative Example 1)
[Manufacture of mask blanks]
The mask blank of Comparative Example 1 was manufactured in the same procedure as in Example 1 except for the phase shift film. As the phase shift film of Comparative Example 1, a single-layer film made of molybdenum, silicon, and nitrogen was applied. Specifically, the translucent substrate 1 is installed in a single-wafer DC sputtering apparatus, and a mixed sintered target of molybdenum (Mo) and silicon (Si) (Mo: Si = 11 atomic%: 89 atomic%). A phase shift film made of molybdenum, silicon, and nitrogen is formed to a thickness of 69 nm by reactive sputtering (DC sputtering) using a mixed gas of argon (Ar), nitrogen (N ₂ ), and helium (He) as a sputtering gas. Formed with.

  Using a phase shift amount measuring device (MPM193, manufactured by Lasertec Corporation), the transmittance and phase difference of ArF excimer laser exposure light of the phase shift film 2 were measured. The transmittance was 6.1% and the phase difference was measured. Was 177.0 degrees (deg). Further, when the optical characteristics of the phase shift film were measured with the above spectroscopic ellipsometer, the refractive index n at the wavelength of the exposure light of the ArF excimer laser was 2.39, and the extinction coefficient k was 0.57. Moreover, the back surface reflectance (reflectance on the translucent substrate 1 side) with respect to light having the wavelength of the exposure light of the ArF excimer laser of this phase shift film was 13%, which was much higher than 9%.

  The mask blank of the comparative example 1 provided with the structure which laminated | stacked the phase shift film which consists of a single layer structure of MoSiN, the light shielding film, and the hard mask film | membrane on the translucent board | substrate with the above procedure was manufactured. In addition, the mask blank of this comparative example 1 has a back surface reflectance of 11.0% with respect to the exposure light of the ArF excimer laser in a state where the phase shift film and the light shielding film are laminated on the translucent substrate, greatly increasing 9%. It was more than.

[Manufacture of phase shift mask]
Next, using the mask blank of Comparative Example 1, a phase shift mask of Comparative Example 1 was produced in the same procedure as in Example 1.

  A simulation of an exposure transfer image when the transferred halftone phase shift mask of Comparative Example 1 is exposed and transferred to a resist film on a semiconductor device with an ArF excimer laser exposure light using AIMS 193 (manufactured by Carl Zeiss). Went. When the exposure transfer image obtained by this simulation was verified, CD variation caused by reflection of a barcode or an alignment mark was observed, and the design specification was not satisfied. From the above, it can be said that the phase shift mask manufactured from the mask blank of Comparative Example 1 cannot perform exposure transfer on the resist film on the semiconductor device with high accuracy.

(Comparative Example 2)
[Manufacture of mask blanks]
The mask blank of Comparative Example 2 was manufactured in the same procedure as in Example 1 except for the phase shift film. In the phase shift film of Comparative Example 2, the thicknesses of the first layer, the second layer, and the third layer are changed to 32 nm, 10 nm, and 25 nm, respectively. In the phase shift film, the thickness of the third layer is 0.78 times the thickness of the first layer, which is less than twice. The refractive index and extinction coefficient of the first layer, the second layer, and the third layer of the phase shift film 2 are the same as those in the first embodiment.

  This phase shift film had a phase difference of 178.4 degrees (deg) and a transmittance of 6.5%. In order that the optical density (OD) with respect to the light of the wavelength (193 nm) of the exposure light of the ArF excimer laser in the laminated structure of the phase shift film and the light shielding film is 3.0 or more, the light shielding film has the composition and optical characteristics. Same as Example 1, but the thickness was changed to 46 nm. The back surface reflectance with respect to the exposure light of the ArF excimer laser of the phase shift film was 35.1%, which was significantly higher than 9%.

  The mask blank of the comparative example 2 provided with the structure which laminated | stacked the phase shift film, the light shielding film, and the hard mask film | membrane on the translucent board | substrate with the above procedure was manufactured. In the mask blank of Comparative Example 2, the ArF excimer laser has a back-surface reflectance of 34.9% for the exposure light in a state where the phase shift film and the light-shielding film are laminated on the light-transmitting substrate, greatly increasing 9%. It was more than.

[Manufacture of phase shift mask]
Next, using the mask blank of Comparative Example 2, a phase shift mask of Comparative Example 2 was produced in the same procedure as in Example 1.

  A simulation of an exposure transfer image when an AIMS 193 (manufactured by Carl Zeiss) is used for exposure and transferred to a resist film on a semiconductor device with an ArF excimer laser exposure light to the prepared halftone phase shift mask of Comparative Example 2. Went. When the exposure transfer image obtained by this simulation was verified, CD variation caused by reflection of a barcode or an alignment mark was observed, and the design specification was not satisfied. From the above, it can be said that the phase shift mask manufactured from the mask blank of Comparative Example 2 cannot perform exposure transfer on the resist film on the semiconductor device with high accuracy.

DESCRIPTION OF SYMBOLS 1 Translucent substrate 2 Phase shift film 21 1st layer 22 2nd layer 23 3rd layer 24 4th layer 2a Phase shift pattern 3 Light shielding film 3a, 3b Light shielding pattern 4 Hard mask film 4a Hard mask pattern 5a 1st resist Pattern 6b Second resist pattern 100, 110 Mask blank 200, 210 Phase shift mask

Claims (23)

A mask blank provided with a phase shift film on a translucent substrate,
The phase shift film includes a structure in which a first layer, a second layer, and a third layer are stacked in this order from the translucent substrate side,
When the refractive indexes at the wavelengths of the exposure light of the ArF excimer laser of the first layer, the second layer, and the third layer are n ₁ , n ₂ , and n ₃ , respectively, n ₁ > n ₂ and n ₂ <n _Satisfying the relationship of ₃
When extinction coefficients at the wavelengths of the exposure light of the first layer, the second layer, and the third layer are k ₁ , k ₂ , and k ₃ , respectively, k ₁ <k ₂ and k ₂ > k ₃ Meet relationships,
When the film thicknesses of the first layer, the second layer, and the third layer are d ₁ , d ₂ , and d ₃ , respectively, the relationship of d ₁ <d ₃ and d ₂ <d ₃ is satisfied. Mask blank to be used. The mask blank according to claim 1, wherein the film thickness d ₃ of the third layer is at least twice the film thickness d ₁ of the first layer. 3. The mask blank according to claim 1, wherein a film thickness d ₂ of the second layer is 20 nm or less. Refractive index _{n 1} of the first layer is 2.0 or more, the extinction coefficient _{k 1} of the first layer is 0.5 or less, less than the refractive index _{n 2} of the second layer is 2.0 The extinction coefficient k ₂ of the second layer is 1.0 or more, the refractive index n ₃ of the third layer is 2.0 or more, and the extinction coefficient k ₃ of the third layer is 0. The mask blank according to claim 1, wherein the mask blank is 5 or less.   The phase shift film has a function of transmitting the exposure light with a transmittance of 2% or more, and the exposure light transmitted through the phase shift film has passed through the air by the same distance as the thickness of the phase shift film. 5. The mask blank according to claim 1, wherein the mask blank has a function of causing a phase difference of not less than 150 degrees and not more than 200 degrees with respect to the exposure light.   The mask blank according to claim 1, wherein the first layer is provided in contact with a surface of the translucent substrate.   The first layer, the second layer, and the third layer are formed of a material composed of silicon and nitrogen, or a material composed of one or more elements selected from a semi-metallic element and a nonmetallic element, and silicon and nitrogen. The mask blank according to claim 1, wherein the mask blank is provided.   The mask blank according to claim 7, wherein the nitrogen content of the second layer is less than the nitrogen content of any of the first layer and the third layer. The phase shift film includes a fourth layer on the third layer,
When the refractive index in the wavelength of the exposure light of the fourth layer was _{n 4,} satisfies the n 1> _{n 4} and _n 3> _{n 4} relationship,
The relation of k ₁ > k ₄ and k ₃ > k ₄ is satisfied, where k ₄ is an extinction coefficient at the wavelength of the exposure light of the fourth layer. The mask blank described. The refractive index of the fourth layer n ₄ is 1.8 or less, the mask blank according to claim 9, wherein the extinction coefficient of the fourth layer k ₄ is characterized in that 0.1 or less.   The fourth layer is formed of a material composed of silicon and oxygen, or a material composed of one or more elements selected from a metalloid element and a nonmetallic element, and silicon and oxygen. Or the mask blank of 10. A phase shift mask provided with a phase shift film having a transfer pattern formed on a translucent substrate,
The phase shift film includes a structure in which a first layer, a second layer, and a third layer are stacked in this order from the translucent substrate side,
When the refractive indexes at the wavelengths of the exposure light of the ArF excimer laser of the first layer, the second layer, and the third layer are n ₁ , n ₂ , and n ₃ , respectively, n ₁ > n ₂ and n ₂ <n _Satisfying the relationship of ₃
When extinction coefficients at the wavelengths of the exposure light of the first layer, the second layer, and the third layer are k ₁ , k ₂ , and k ₃ , respectively, k ₁ <k ₂ and k ₂ > k ₃ Meet relationships,
When the film thicknesses of the first layer, the second layer, and the third layer are d ₁ , d ₂ , and d ₃ , respectively, the relationship of d ₁ <d ₃ and d ₂ <d ₃ is satisfied. Phase shift mask. It said third layer thickness d ₃ of the phase shift mask according to claim 12, wherein the at first layer 2 times or more the thickness d ₁ of the. 14. The phase shift mask according to claim 12, wherein a film thickness d ₂ of the second layer is 20 nm or less. Refractive index _{n 1} of the first layer is 2.0 or more, the extinction coefficient _{k 1} of the first layer is 0.5 or less, the refractive index _{n 2} of the second layer is less than 2.0 The extinction coefficient k ₂ of the second layer is 1.0 or more, the refractive index n ₃ of the third layer is 2.0 or more, and the extinction coefficient k ₃ of the third layer is 0. The phase shift mask according to claim 12, wherein the phase shift mask is 5 or less.   The phase shift film has a function of transmitting the exposure light with a transmittance of 2% or more, and the exposure light transmitted through the phase shift film has passed through the air by the same distance as the thickness of the phase shift film. 16. The phase shift mask according to claim 12, which has a function of causing a phase difference of 150 degrees or more and 200 degrees or less with respect to the exposure light.   The phase shift mask according to claim 12, wherein the first layer is provided in contact with a surface of the translucent substrate.   The first layer, the second layer, and the third layer are formed of a material composed of silicon and nitrogen, or a material composed of one or more elements selected from a semi-metallic element and a nonmetallic element, and silicon and nitrogen. The phase shift mask according to claim 12, wherein the phase shift mask is provided.   19. The phase shift mask according to claim 18, wherein the nitrogen content of the second layer is less than the nitrogen content of any of the first layer and the third layer. The phase shift film includes a fourth layer on the third layer,
When the refractive index in the wavelength of the exposure light of the fourth layer was _{n 4,} satisfies the n 1> _{n 4} and _n 3> _{n 4} relationship,
20. The relationship of k ₁ > k ₄ and k ₃ > k ₄ is satisfied, where k ₄ is an extinction coefficient at the wavelength of the exposure light of the fourth layer. The phase shift mask as described. The refractive index of the fourth layer n ₄ is 1.8 or less, a phase shift mask according to claim 20, wherein the extinction coefficient k ₄ of the fourth layer may be equal to 0.1 or less.   21. The fourth layer is formed of a material composed of silicon and oxygen, or a material composed of one or more elements selected from a metalloid element and a nonmetallic element, and silicon and oxygen. Or the phase shift mask of 21.   23. A method of manufacturing a semiconductor device, comprising using the phase shift mask according to claim 12 and exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate.

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